How old is your baby? My DD2 is now 7 1/2 months old, so I can sympathize with a lot of what you say. She has actually slept well this night, but has been snuffling, snoring and occasionally making noises like she's about to cry, so I haven't slept at all well.
Lack of sleep can affect you badly, and you don't even realise that it's doing so, or that that's the reason. Add worry about the op and about DD2 on top of that, not a fun time.
It will pass though. Once the op is out of the way, I hope you feel like a weight is lifted. The sleep may take more time, but it will come.
Try not to compare yourself to other people - that way lies madness. Plus, you have no idea how well they're really coping, just how well they let people think they are. Anyone can put on a veneer of coping well to show the outside world.
For the weight thing - if you really want to do something about it, make up your mind to do it. I've found that the first step is to decide to do it, and that the willpower that comes from the decision is the most important thing. If you're not ready yet, don't beat yourself up about it, you have enough on your plate.
I found myfitnesspal very useful, thanks to MN recommendations. Just the calorie counting bit helped me limit intake and cut down the comfort eating. I'm not exactly on a diet, I've just cut right down on the cake and chocolate I was eating (and letting myself get away with because I was BFing). I have a generous 2000 calories a day, and still manage to lose 1-2 lb a week, and am below my pre-DD2 weight, hoping to get down to my pre-DD1 weight by DD2's first birthday.
Sorry for the long post, but I hope it helps. Good luck!